This invention concerns a method and a device for weed control by means of electricity.
For many years the use of weed poisons, in addition to purely mechanical methods, has been the dominating method for weed control. There is increasing concern that an extensive use of weed poisons may harm the environment as well as humans and animals. This concern has led to an increasing interest for alternative non-chemical methods as a complement to the traditional mechanical methods.
The concept of killing weed by means of electric energy has been used since the 1890's when "Vegetation exterminators" was patented (Sharp, A. A. 1893, Scheible, A. 1895) The technique was also developed also for weed control in the agriculture (Buret, W. E. 1928, Opp, F. W. ; Collins, W. C. 1935, Opp, F. W. 1952, Poynor, R. R. 1954). It has been further suggested for use in farming, in particular non-specific superficial treatment of the soil by moving electrodes along the ground surface and applying an alternating voltage (Laronze 1982) or constant high voltage (Krause 1975).
Equipment using electric current for pruning of blueberry bushes and dehydration of the foliage of root crops before harvest has been suggested by (Plueneke, R. H. ;Dykes, W. G. 1975, Plueneke, R. H. ;Dykes, W. G. 1977).
Thinning out of drilled plants was suggested in the 1950's by (Rainey, E. C. 1952, McCreight, N. L. 1953). Use in soil sterilizing and fertilizing has also been suggested (Keller, C. R. 1947, Opp, F. W.; Collins, W. C. 1935). Wayland et al (1975) showed that technically one can use micro waves for sterilizing soil before sowing. Weed and weed seed a few cm into the ground can be killed with microwaves having a frequency of 2450 MHz and the power 60 kW. The machine used was a 150 kW diesel driven generator that fed a microwave generator and a hydraulic system that slowly moved the equipment forward. Dipose et al. (1984) estimated that it would take between 100-1000 hours per feature to treat some types of weeds. Such long times are unavoidable. The machine radiates microwaves down into the ground to heat everything and must literally boil the weed which requires a great deal of energy. A further drawback is that also the micro flora in the soil is knocked out.
As is apparent from the above it has not yet turned out to be practical to use electricity for weed control. It is quite simply too expensive and time consuming in relation to chemical and mechanical control methods.